Our research has been addressed in developing subtype-selective ligands for the Thyroid Hormone Receptor (TR). The lead compound we synthesized, GC-1, revealed interesting and potentially useful thyromimetic properties. This new compound, structurally related to the natural hormone T3, is a high affinity ligand for the TR and shows subtype selectivity for TR-beta over TR-alpha in both receptor binding and ligand-activation function. T3 is not subtype selective. The crystal structure of TR-beta ligand binding domain (LDB) bound with GC-1, TR-beta LDB bound with T3 and TR-alpha-1 LBD bound with T3 have been solved Visual inspection of these structure with the program MidasPlus and using the Computer Graphics Laboratory facilities has been essential in understanding the molecular basis for GC-1 subtype selectivity.